1. Field of the Invention
The present invention relates to a curl correcting apparatus for correcting curling of a rolled sheet material.
2. Related Background Art
The recording system of various office equipment such as a facsimile or printer generally employs a continuous web-shaped recording sheet wound in a roll form.
Because of the rolled form, the sheet material tends to show curling. For this reason there have been proposed technologies for removing or reducing said curling.
As an example of said technologies, FIG. 23 illustrates a curl eliminating apparatus, in which a main body 1 and a cover 2 are mutually articulated movably by a pin 3. In the main body 1 there are provided a roll holder 4, a platen roller 5, a cutter 6 and a guide member 7a constituting the curl eliminating device, while the cover 2 holds a recording head 8 and a guide member 7b constituting the curl eliminating device in cooperation with the guide member 7a. Said roll holder 4 supports a roll 9a of the sheet material 9.
The sheet material 9 fed from said roll 9a is transported by the platen roller 5, and the curl is removed in passing an acute angled path formed by the guide members 7a, 7b. Then the sheet is subjected to image formation by the recording head 8, cut by the cutter 6 and discharged from the apparatus.
In the conventional structure shown in FIG. 23, the sheet material 9 remains bent between the guide members 7a, 7b in the stand-by state of the apparatus. Thus the sheet material 9 between said guide members 7a, 7b generates curling in a direction opposite to that generated by winding, and such curling may give rise to troubles such as sheet jamming. Also the guide members 7a, 7b of fixed angle may be unable to adequately remove the curling which varies according to the diameter of the roll 9a .
FIG. 24 illustrates another example of the already proposed curl removing apparatus. The clockwise rotation of the platen roller 5 is transmitted, through a frictional clutch, to a guide shaft 10 and arms 11 provided on both ends of said shaft 10. At the outer end of the arms 11, there is rotatably supported a curl correction shaft 12. In predetermined positions of the main body 1, there are fixed stoppers 13, 14 for limiting the movement of the arms 11, which is constantly biased toward the stopper 13 by means of a spring.
The sheet material 9 is transported by the platen roller 5, of which rotation is transmitted to the guide shaft 10 thereby rotating the arms 11 clockwise. When the arms 11 impinge on the stopper 14, the rotation of the arms 11 is stopped by the slippage of the frictional clutch. The sheet material 9 is bent in acute angle in a path from the roll 9a, through the guide shaft 10, to the curl correction shaft 12 for curl correction, and is then transported to the platen roller 5.
When the rotation of the platen roller 5 is terminated, the arms 11 rotate anticlockwise by the biasing force of the spring and returns to the position in contact with the stopper 13.
In this conventional structure, the curling on the sheet material 9 is removed by the guide shaft 10 and the curl correction shaft 12 mounted on the arms 11 rotated by the transportation of the sheet material 9.
In the conventional structure shown in FIG. 24, in loading a new roll 9a in the roll holder 4, the leading end of the sheet material 9 has to be threaded between the guide shaft 10 and the curl correction shaft 12, so that a cumbersome some operation is required. Also the sheet material 9 subjected to curl correction by the shaft 12 shows a large wrapping angle on the platen roller 5, thus eventually developing curl again. Also in the standby state of the apparatus, the sheet material 9 hangs down between the platen roller 5 and the roll 9a, thereby curl opposite to the curl of rolling. Also the main body 1 has to be made larger in order to accommodate the rotation of the arms 11 about the guide shaft 10 for curl correction of the sheet material 9.
Also the curl correction apparatus disclosed in the Japanese Patent Laid-open No. 55-15381 is associated with a drawback of curl generation opposite to the curl by rolling, since the sheet material remains bent for curl correction in the stand-by state of the apparatus.